Movable contact structure for an electric switch

ABSTRACT

A movable contact structure for a large size electric switch which is arranged so the contacts of the switch may be readily inspected. The contact structure includes a movable contact retainer that has apertured ears and the base of the switch which supports the stationary contacts includes support posts, which, when the switch is disassembled to inspect the contacts, are available to act as a fulcrum for the shank of a screwdriver when the tip of the screwdriver is inserted into the apertures. The screwdriver thus may be used as a tool to overcome the spring forces holding the movable contact retainer and thus facilitate the removal and replacement of the movable contacts from its position on the movable contact carrier.

United States Patent Puetz Feb. 29, 1972 [54] MOVABLECONTACT STRUCTURE 9,544,929 12/1910 m Marco et a1 .1335/132 FOR AN ELECTRIC SWITCH Primary Examiner-Harold Broome Attorney-Harold J. Rathbun and William H. Schmeling [5 7] ABSTRACT A movable contact structure for a large size electric switch which is arranged so the contacts of the switch may be readily inspected. The contact structure includes a movable contact retainer that has apertured ears and the base of the switch which supports the stationary contacts includes support posts. which, when the switch is disassembled to inspect the contacts, are available to act as a fulcrum for the shank of a screwdriver when the tip of the screwdriver is inserted into the apertures. The screwdriver thus may be used as a tool to overcome the spring forces holding the movable contact retainer and thus facilitate the removal and replacement of the movable contacts from its position on the movable contact carrier.

8 Claims, 3 Drawing Figures PATENTEUFEB29 I972 m m m N I v JORDAN F. PUETZ MOVABLECONTACTSTRUCTUREFOKAN ELECTRIC SWITCH;

The presentinvention relates toswitching devices and more particularlyv totheidetailsof construction of a movablecontact structure andsupporttherefor in an electric switch.

g The contactstructure of thetypewith which therpresent invention is concerned isparticularly. suited for use in .elec-.

tromagneticswitchingdevicescommonly known as contactors which, are fumished as devices of .varying sizes having ratings in accordance-with the standards promulgated by the National Electrical. Manufacturers Association, commonly known as NEMA-. lt is wellknownthat.anyconductor is heated by thecurrent passing throughthe conductor and therefore it follows.

thatanincreasein the currentcarrying capacity .of a device requires acorresponding increasein the cross-sectional mass horizontal position whenthe-contactor. ismounted :onafront I lies .uponan abutting. engagement between a stationaryand av movablecontact structure to complete an electric circuit will.

operatewith, a phenomenon known as contact bounce.

Further,- in anyswitching device the current conducting,

capacity betweemthe stationary andthemovable contactsurfaces .is dependent-upon the: area of surfacecontact and the pressure between the abutting surfaces. Thus as the size of the switches ;isprogressively increased, the forcesof the springs. usedin the movable-contact structure must be progressively increased-to minimize thecontact bounce and maximize the; current conducting capacity of the switch. Acceptable maintenance practices require that occasionally the contacts of the,

switches of thetypewith which the'present invention is concerned.,,be-.,-.inspected for; wear and thatthe contacts be. replaced when necessary.;ln smaller size switches usually the replacement is accomplished with minimum difficulty. How.- ever, in largersized-devices, the forces exerted ,by the springs on the retainers which maintainthe movable contacts in their proper. position, make; the .removal and-replacement of the- 5 movable contacts difi'lcult fl'hepresent-invention-relates to a movable- =.contac.tretainerstructuresand a switch structure wherein the movable. contacts may be: readily. inspected and removed and replaced with'out difficulty.-.

It is an, object of the:present invention to provide a movable contact retainer structure in an electricswitchwhich will permit thecontactsto bereadilyinspected and serviced;

An additional objectis to provide. an. electric, switch with amovable contact-structure that includes a contact-carrier havingaportion movablein a slot in an insulating base and pot-- tionsextendingthroughopenings in the base, to a front surface of provides support surface .whereon a movable contactjspositionedand. to connect themovablc contact to 1 .theicarrierby-a spring biased retainer thatthas apertured ears and to provide the base with mountingposts which serve as a fulcrumv for theshank of a screwdriver when the tip of the screwdriver is inserted in theapertured ears for the purpose of movingrthe retainer to a retracted positionwhile the movable contact is removed or installed on-the support surface.

Further: objects ,and features of the inventionwill bereadily apparent to those skilledin the art-from the specification and appended drawing illustrating a preferred embodiment in which:.

FIG. 1 is a perspective view of an electric switchincorporating a movable contact. retainer-structure according to the,

present invention.

FIG; 2 is a cross-sectional view of a base. includingthe Sta-- FIG. 3 is a perspective .view of-the movable contact and switch or contactoris described herein as disposed in a wall of a vertical panel, the-parts of 'the.- contactor-;-being1-.

described in relation to this position. Accordingly, theterms front. andrear, upper and lower, vertical and horizontaland;

thelike'are not absolute but merely define more-readily .-the.-. relativepositionsof portions of the partsandtheir relative positions to each other whenthe contactor is mounted-.on1acomponents of the assembly. 10 includea metal. mountinga plate 12,, an insulating .base 14, and insulating: barrier 16, a.

metalshock plate l8,-an electromagnet assembly 20,.a metal cover- 22 and a movablecontact carrier 24; Thedetails of constructionofthebarrier .16 and. the shock plate. 181are clearly set forth in an applicationfor U.S. Pat., Ser. No. 99,613, concurrently filed herewith. .The details of constructionof theelectromagnet assembly 20; as well, as the arrangement. for maintaining the electromagnet, assembly-20 in the switcharc. disclosed in an application for patent having a Ser. No. 99,6l4, concurrently filed herewith. Similarly, the construc@ tional detailsof the cover 22 andthe arrangement--for.con.--- necting thearmature of the electromagnet assembly 20 to the. movablecontact carrier 24 are respectively shown in applica tions for U.S. Pat, Ser. Nos. 99,573 and. 99,574,. which similarly are concurrently filed herewith.

The mounting plate 12 is fonned in a stamped metal P8110 provide a means to secure the switch assembly-l0 to a vertical panel and the'like, not shown. When the plate l2-is securedto the panel, art-edge 26 becomes the bottomedge of the plate.12 and a surface 28 the front surface of the platev 12; The plate '12. hasa pair of rearwardly extending indentations 30 along its. bottom edge 26 that provide a pair of spaced mounting-feethaving openings therein. The plate 12 also has an indentation 31 at its :top edge, which provides an elongated-mounting foot having an opening thereinwhich, together with the indenta-.

tions 30,.are provided for the purpose of securing theplate- 12 :1

l4-is furnished with three sets of stationary contactsand,

movable contacts which are duplicates of the single set.s'ta-,- tionary contacts and the movable contact shown .-in FIG; 2. i The base 14 and the barrier16are formed of a molded insulat ing material having arc suppressing capabilities and cooperatewith each other to provide. three compartmentswhich extendv in parallel between the top and the bottom of the switch 10.- Positioned in each compartment isa set of stationary contacts, and a movable contact. The base. 14 hasa rearsurface 32 positioned ontheiplate 12 by suitable screws which passthrough. I openings in the base- 12' and are threadedly received-in threaded inserts. which are embedded in the material of the plate 12., Extending in thebase -14 forw'ardlyof .therear sur--. face 32 and throughthe side walls of thebase 14 a slot The; slot34 is centered'in a centerline equidistantxbctween a top wall 36 and a bottom wall 38 of -the,base.l4 and is exposed to each of thecompartments in the base 14by'a passage 40? Positioned onopposite sides a of the passage 40 "so as to be equidistant from a vertical plane through the center of the; passage 40 is a pair of stationary contact assemblies 42 and which are identical. Each of the assemblies 42 and-44 includes a temtinal member which is arranged to accept'a bared end i of a wire conductor, a conductingbarlike memberAS and a". support -50 for -.a 'noble'metal piece that provides-astationary. contact surface -52.'The members 46 and 48 'arepositioned on. a front wall 54 of thebase-l4 by a screw-56 whichextends-m through openingsin the member'46-and48 intoa threaded'in sert58whichis embeddedin the frontwall.54. 'lhe support:50

is securedto the member 48 by a screw 60211116 support 501s shapedso thecontactsurface SZIisinclinedandfaces the ver-zr tical plane throughtthercenter of the passage;

The movable contact carrier 24 is formed of a molded insulating material and is generally U-shaped, having a bight or body portion 64 received so as to be movable in the slot 34 and arm portions 66 extending externally of the side walls of the barrier 16. The arm portions 66 are connected to an armature 68 of the electromagnet assembly 20 and are moved rearwardly toward the plate 12 when the electromagnet is energized so that the bight portion 64 is moved rearwardly in the slot 34. A pair of compression springs 70 positioned between the rear wall of the bight portion 64 and the plate 12 position the bight portion 64 forwardly in the slot 34 when the electromagnet is deenergized. Extending through each of the passages 40 is a projection 72. The projections extend from the bight portion 64 to present a forwardly facing support surface 74 that is spaced forwardly of the front wall 54 of the base 14. Each projection 72 is rectangular in shape and has a rectangularly shaped cavity 76 extending from an open end at the rear wall of the bight portion 64 to a rearwardly facing spring seat 78 that is spaced rearwardly of the support surface 74. Extending through the material of the projection between the support surface 74 and the spring seat 78 are a pair of openings 80. The openings 80 are rectangular in shape and located along opposite sides of the surface 74 so the side walls 82 of the cavity in effect extend to the surface 74. If desired, a pair of spaced walls 84 extending parallel to the openings 80 may be provided to project from opposite sides of the projection 72 forwardly of the support surface 74.

Positioned on the support surface 74, when the electromagnet 20 is deenergized, is a movable contact 86. The movable contact 86 has a central portion 88 resting on the support surface 74 and a pair of arms 90 which extend generally in op posite directions from the central portion 88. The arms 90 are inclined and each has a noble metal portion secured thereon to present contact surfaces 92 which engage the contact surfaces 52 when the movable contact carrier 24 is moved rearwardly toward the plate 12 upon the energization of the electromagnet 20.

A means for removably positioning the movable contact 86 on the support surface 74 includes a U-shaped member 94, a metal part 96 and a spring 98. The U-shaped member 94 has a bight portion 100 resting on the central portion 88 and a pair of arms 102 extending from the bight portion along opposite sides of the central portion 88 through the openings 80 so that a portion 104 of the arms 102 is received within the cavity 76 in close proximity to the walls of the cavity 76. The walls of the cavity 76 and the openings 80 thus act as guides for the movement of the arms 102. Each portion 104 has a rectangular slot 106 therein. The slot 106 is located in the portions 104 to present a support portion 108 at the free ends of the arms 102. The metal part 96 has its opposite ends resting on the support portions 108 of the pair of arms 102 so a central portion on the part 96 provides a bridge between the free ends of the pair of arms and a seat 1 for an end of the spring 98 that has its opposite end resting against the spring seat 78. The spring 98 is thus positioned to urge the metal part 96 and the U-shaped part 94 rearwardly so that the bight portion 100 is constantly pressed into tight engagement with the central portion 88.

The movable contact 86 is further held against displacement from beneath the bight portion by a projection 112 which extends forwardly from the central portion into a centrally located opening in the bight portion 100. The energization of electromagnet assembly causes the movable contact carrier 24 to move rearwardly to a position wherein the contact surfaces 92 engage the contact surfaces 52. When the carrier is at its furthest rearward position, the central portion 88 will be separated from the support surface 74 and the force provided by the spring 98 on the metal part 96 and the U- shaped part 94 on the central portion 88 will cause the contact surfaces 52 and 92 to be pressed into a finn engagement with each other. I

Extending forwardly from the front wall 54 on the base 14 are four spaced posts 114 each of which has a front surface 116 whereon the shock plate 18 is mounted by four screws 118 in a manner illustrated in FIG. 1. The barrier 16, which is suspended from the shock plate 18 by four screws 120, as illustrated by FIG. 1, has its rear edge juxtaposed but not engaging the front wall 54 and includes rearwardly extending barriers which extend parallel to each other between the top and bottom of the barrier 16 so as to provide the three spaced compartments wherein the three movable and stationary contact assemblies of the switch 10 are received. The free ends of the arm portions 66 of the movable contact carrier 24 are.

secured to the armature 68 by a pair of screws 122 in a manner illustrated in FIG. 1. Thus access to the stationary and movable contacts of the switch 10 is readily obtained by removing the four screws 118 and the pair of screws 122 so that the assembly, including the shock plate 18, the barrier 16,. the electromagnet assembly 20, as well. as the cover 22, is removed as a unit from the base 14 while the movable contact carrier 24 remains assembled with the base 14. The removal of the shock plate 18 and the components assembled thereto will expose the front wall 54 and the stationary contacts assemblies 42 and 44 as well as the movable contacts 86 for inspection. The replacement of the stationary contacts is readily accomplished by removing the screws 60 and the supports 50 and substituting new supports 50 and replacing the screws 60.

The replacement of the movable contacts is facilitated by the presence of the mounting posts 114 and a pair of cars 124 that are formed to extend forwardly on the top and bottom edges of the bight portion 100. The cars 124 each have an aperture 126 therein. The apertures 126, together with the surfaces 116, provide a means whereby the force exerted by the springs 98 may be overcome and the bight portion may be moved out of its engagement with the central portion 88. As illustrated by the broken lines in FIG. 2, the posts 114 provide a fulcrum for a shank of a tool, such as a screwdriver 128, which has its tip positioned in the aperture 126 in one of the ears 124. When the screwdriver 128 is thus positioned and a force applied, the U-shaped part 94 and the metal part 96 will move against the bias of the spring 98 and be temporarily held in a position wherein the bight portion 100 is spaced from the central portion 88 so the movable contact 86, which is to be replaced, may be slid from its position between the bight portion 100 and the surface 74 and a new movable contact 86 be installed in j the position previously occupied by the removed removable contact 86.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In an electric switch, the combination comprising: an insulating base having a front surface, a rear surface, a passage extending between the front surface and the rear surface and a pair of stationary contacts mounted on the front surface respectively equidistantly on opposite sides of the passage, an insulating movable contact carrier having a body portion movable in the passage and projecting through the passage to present a forwardly facing support surface that is spaced forwardly of the front surface, a cavity extending from a rear wall of the body portion into the projection and providing a rearwardly facing spring seat that is spaced rearwardly of the support surface, and a pair of openings in the support surface respectively extending along opposite sides of the surface into the cavity, a movable contact having a central portion positioned on the support surface, a pair of arms respectively extending from opposite sides of the central portion to present contact surfaces that are engageable with the stationary contacts when the body portion is moved to a predetermined position in the passage, and a means for removably positioning the central portion on the support surface includinga U-shaped member having a bight portion engaging a front surface'on the central portion, a pair of arms extending through the openings to present a portion on each arm within thecavity, and a slot in each arm portion within the cavity, a metal part having its opposite ends respectively extending into the slots and a central portion that provides a spring seat located between the arms and a spring having its opposite ends positioned on the spring seat in the cavity and the, spring seat on the metal part for constantly urging the bight portion against the central portion.

2. The combination as recited in claim 1 including at least one apertured ear forwardly extending from a side of the bight portion and at least one post forwardly extending on the base, said post providing a fulcrum for a shank of a screwdriver when a tip of the screwdriver is inserted in the aperture for the purpose of removing and installing the movable contact on the support surface.

3. The combination as recited in claim 1 wherein the cavity and the openings in the body portion have a rectangular shape so that the wall portions of the cavity and the openings provide guide surfaces for the arms of the U-shaped member when the U-shaped member is moved against the force provided by the spring.

4. The combination as recited in claim 2 wherein the cavity and the openings in the body portion have a rectangular shape so that the wall portions of the cavity and the openings provide guide surfaces for the arms of the U-shaped member when the U-shaped member is moved against the force provided by the spring.

5. The combination as recited in claim 1 including a pair of apertured ears respectively forwardly extending from opposite sides of the bight portion and a pair of posts forwardly extending on the base, said posts providing a fulcrum for a shank of a screwdriver when a tip of the screwdriver is inserted into one of the apertures for the purpose of removing and installing the movable contact on the support surface.

6. The combination as recited in claim 2 including at least one spring having an end engaging the body portion for urging the contact carrier to a position wherein the movable contact is separated from the stationary contacts.

7. The combination as recited in claim 2 wherein the contact carrier includes a main portion that is movable in a slot in a rear wall of the base, the body portion extends from the main portion through the passage and the cavity extends from a rear wall-of the main portion into the body portion.

8. The combination as recited in claim 2 wherein the slots are elongated so that the metal part is movable between the arms of the U-shaped member.

' a a a :r 

1. In an electric switch, the combination comprising: an insulating base having a front surface, a rear surface, a passage extending between the front surface and the rear surface and a pair of stationary contacts mounted on the front surface respectively equidistantly on opposite sides of the passage, an insulating movable contact carrier having a body portion movable in the passage and projecting through the passage to present a forwardly facing support surface that is spaced forwardly of the front surface, a cavity extending from a rear wall of the body portion into the projection and providing a rearwardly facing spring seat that is spaced rearwardly of the support surface, and a pair of openings in the support surface respectively extending along opposite sides of the surface into the cavity, a movable contact having a central portion positioned on the support surface, a pair of arms respectively extending from opposite sides of the central portion to present contact surfaces that are engageable with the stationary contacts when the body portion is moved to a predetermined position in the passage, and a means for removably positioning the central portion on the support surface including a U-shaped member having a bight portion engaging a front surface on the central portion, a pair of arms extending through the openings to present a portion on each arm within the cavity, and a slot in each arm portion within the cavity, a metal part having its opposite ends respectively extending into the slots and a central portion that provides a spring seat located between the arms and a spring having its opposite ends positioned on the spring seat in the cavity and the spring seat on the metal part for constantly urging the bight portion against the central portion.
 2. The combination as recited in claim 1 including at least one apertured ear forwardly extending from a side of the bight portion and at least one post forwardly extending on the base, said post providing a fulcrum for a shank of a screwdriver when a tip of the screwdriver is inserted in the aperture for the purpose of removing and installing the movable contact on the support surface.
 3. The combination as recited in claim 1 wherein the cavity and the openings in the body portion have a rectangular shape so that the wall portions of the cavity and the openings provide guide surfaces for the arms of the U-shaped member when the U-shaped member is moved against the force provided by the spring.
 4. The combination as recited in claim 2 wherein the cavity and the openings in the body portion have a rectangular shape so that the wall portions of the cavity and the openings provide guide surfaces for the arms of the U-shaped member when the U-shaped member is moved against the force provided by the spring.
 5. The combination as recited in claim 1 including a pair of apertured ears respectively forwardly extending from opposite sides of the bight portion and a pair of posts forwardly extending on the base, said posts providing a fulcrum for a shank of a screwdriver when a tip of the screwdriver is inserted into one of the apertures for the purpose of removing and installing the movable contact on the suPport surface.
 6. The combination as recited in claim 2 including at least one spring having an end engaging the body portion for urging the contact carrier to a position wherein the movable contact is separated from the stationary contacts.
 7. The combination as recited in claim 2 wherein the contact carrier includes a main portion that is movable in a slot in a rear wall of the base, the body portion extends from the main portion through the passage and the cavity extends from a rear wall of the main portion into the body portion.
 8. The combination as recited in claim 2 wherein the slots are elongated so that the metal part is movable between the arms of the U-shaped member. 